Toronto: The younger an immigrant, the higher the risk of developing inflammatory bowel disease (IBD) and its major subtypes - Crohn's disease and ulcerative colitis - says a Canadian study.

While immigrants to Canada have lower rates of IBD compared to Canadian-born residents, that risk goes up in immigrants who are younger at arrival to Canada, the researchers noted.

"These findings suggest an increased risk of IBD when there is early-life exposure to the Canadian environment in immigrants from some regions," said Eric Benchimol, pediatric gastroenterologist at Children's Hospital of Eastern Ontario (CHEO).

Canada has one of the highest rates of IBD in the world and the new findings suggest that the environment plays an important role in IBD pathogenesis.

While their parents were at lower risk of developing IBD, once they arrive the children of immigrants from the Middle East, North Africa and South Asia had the same incidence of IBD compared with the children of non-immigrants.

In fact, there is a 14 per cent increased risk per younger decade of life at immigration, the findings of the population-based study showed.

However, the children of immigrants from East Asia, Eastern Europe, Central Asia, Latin America and the Caribbean had lower incidence of IBD compared with the children of non-immigrants.

"IBD is a disease of Westernized nations, with high rates in North America and Europe, and low rates in Asia, Africa, and South America," Benchimol noted.

"Rates increased dramatically in Eastern Europe in recent decades and are increasing in other nations as Western lifestyle becomes more prevalent," Benchimol cautioned.

The researchers studied immigrants to Ontario, Canada, by region of birth between 1994 and 2010.